linux-kernel - Re: [PATCH] crypto: xts,lrw - fix out-of-bounds write after kmalloc failure

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Message-Id: <20170323.140514.85099184426140784.davem@davemloft.net>
Date:   Thu, 23 Mar 2017 14:05:14 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     ebiggers3@...il.com
Cc:     linux-crypto@...r.kernel.org, herbert@...dor.apana.org.au,
        linux-kernel@...r.kernel.org, dvyukov@...gle.com,
        syzkaller@...glegroups.com, ebiggers@...gle.com,
        stable@...r.kernel.org
Subject: Re: [PATCH] crypto: xts,lrw - fix out-of-bounds write after
 kmalloc failure

From: Eric Biggers <ebiggers3@...il.com>
Date: Thu, 23 Mar 2017 13:39:46 -0700

> From: Eric Biggers <ebiggers@...gle.com>
> 
> In the generic XTS and LRW algorithms, for input data > 128 bytes, a
> temporary buffer is allocated to hold the values to be XOR'ed with the
> data before and after encryption or decryption.  If the allocation
> fails, the fixed-size buffer embedded in the request buffer is meant to
> be used as a fallback --- resulting in more calls to the ECB algorithm,
> but still producing the correct result.  However, we weren't correctly
> limiting subreq->cryptlen in this case, resulting in pre_crypt()
> overrunning the embedded buffer.  Fix this by setting subreq->cryptlen
> correctly.
> 
> Fixes: f1c131b45410 ("crypto: xts - Convert to skcipher")
> Fixes: 700cb3f5fe75 ("crypto: lrw - Convert to skcipher")
> Cc: stable@...r.kernel.org # v4.10+
> Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>

Acked-by: David S. Miller <davem@...emloft.net>